Soil health begins with understanding the soil biota, according to Janice Thies, associate professor of soil biology at Cornell University. She presented about the importance of critters that live in soil at the recent Empire Farm Days.
“Biota provides ecosystem services, including benefits like decomposing organic matter, release and cycle nutrients, nitrogen fixation, and mycorrhizae fungi,” Thies said.
She added that biota also suppresses disease and improves soil structure — the ability of soil to hold together under rainfall impact. That is an important benefit, since it promotes water filtration and storage. Biota also consumes greenhouse gasses in the air and reduces the greenhouse gasses emitted.
“Ag systems are under pressure about how to reduce greenhouse gas production,” Thies said. “They are a genetic reservoir.”
But biota also have a few caveats. They can immobilize nutrients and cause disease, for example.
“Energy is critical to microbial survival and function in the soil environment,” Thies said.
Biological activity’s primary limiting factors include energy supply, such as light penetration for plants and substrate quality and availability for soil organisms, plus functioning as a source of cell carbon, such as carbon dioxide for plants and organic carbon for most soil organisms.
“For some organisms, they can fix their own carbon dioxide,” Thies said.
Soil organisms can help with nutrient cycling, soil aggregation, plant protection, plant productivity, detoxification and organic matter formation. Within the soil, nematodes, fungi and bacteria all have positive and negative functions affecting plants.
“We have parasitic nematodes that are up to no good,” Thies said.
These are the nematodes farmers should work to suppress. But beneficial nematodes can check the proliferation of harmful agents and break down organic material.
Plants and the microbiome in the soil share “a really nice symbiotic relationship,” Thies said.
Plants take in carbon dioxide and release food for soil organisms. Soil organisms provide enzymes, minerals, antibiotics, growth regulators and hormones to feed plants.
Bacteria decompose organic matter, move nutrients and control pathogens. But bacteria gone rogue can also cause plant diseases.
“The number one thing you need is to have the soil turned over,” Thies said. “A lot of things we count on include inoculants and cultural control.”
The former includes nitrogen fixing bacteria, phosphorus solubilizing, microbial soups, compost teas and signal molecules alone. The latter includes adding organic matter, reducing toxins, keeping plants in the system with cover crops, oxygenating the soil and improving drainage.
“All these systems are controlled by bacteria,” Thies said. “We have decades of success with legume/rhizobium symbiosis. We have been inoculating plants since the early 1900s.”
To promote overall soil health, Thies said that farmers have many tools, such as using compost to feed soil organisms.
“They need to eat so they can work for you,” Thies said.
She added that fungi also play a role in soil health, since they decompose organic matter, mobilize phosphorus, control pathogens, promote plant growth, control insects and aggregate and stabilize soil.
“These are all very important functions,” Thies said. “Try to reduce toxins like fungicides. For the most part, fungi are your friends.”
Reducing tillage and avoiding bare fallow fields also help.
While many beneficial agents in the soil are tiny, larger ones like earthworms, sow bugs, mites and dung beetles also help enrich the soil through things like simulating microbial activity, mixing soil, increasing water filtration, and breaking down organic matter. Reducing tillage and chemicals while increasing organic matter can encourage the growth of these soil helpers.
“We need to think about how to promote beneficials and reduce the impact of those that aren’t,” Thies said. “We need to think about gas and water exchange.”
At Cornell, Thies focuses her study on soil ecology as an indicator of soil biological quality, remediation of degraded soils and sustainable soil management.